Process of purifying gelatin and casein



Patented Feb. 20, 1940 Charles Schwartz, Pittsburgh, Pa., assignor to Hall Laboratories, Inc., Pittsburgh, Pa., a corporation of Pennsylvania No Drawing.

Application September 24, 1937,

7 Serial No. 165,479

1'7 Claims. (Cl. 260-118) This invention relates to the purification of gelatin and casein, and the present applicationis a continuation-in-part of my application Serial No. 752,996, filed November 14, 1934.

5 The demand for gelatin and casein in many fields has resulted in numerous methods for their extraction and preparation. In nearly all the methods there is involved the addition of agents for precipitation, filtration, clarification, extrac- 1 tion, etc. These additions result very often in the contamination of the final product with the reagents which have been used. Furthermore,

gelatin and casein are often combined or associated with impurities which it is diificult to remove by the processes of purification which are now known.

In accordance with the present invention, ma-

terials containing gelatin or casein are purified" uble form commonly known as hexametaphos phate. The material which I prefer to use in the purification of gelatin and casein is the soluble sodium hexametaphosphate sometimes called "Grahams salt." This may have mixed with it a small amount of sodium pyrophosphate to counteract the slight acidityof the sodium metaphosphate. There may also be mixed with the sodium metaphosphate or the mixture of sodium metaphosphate and pyrophos-- Phate, small quantities of alkalies such for example as sodium carbonate, sodium bicarbonate,

borax, trisodium phosphate, or sodium metasilicate, these alkalies likewise being added for the purpose of counteracting the slight acidity of the sodium metaphosphate and constituting only a small proportion of the mixture.

I may also employ as the purifying material an alkali-metal tripolyphosphate such for example as sodium tripoiyphosphate (NasPaOio) .50 either alone or in admixture with an alkali-metal meta-phosphate. If mixtures are employed, they may have added to them small amounts of alkaline materials, as previously described. Sodium tripolyphosphate is the most important ofthe as alkali-metal tripolyphosphates. Crystalline sodium tripolyphosphate is a definite chemical compoundof the formula NasPsOm in its anhydrous form. It may also be prepared as a crystalline hydrate. It is not deliquescent and particularly in the hydrated form inay be preserved 5 indefinitely in ordinary atmospheres without caking or picking up moisture. It may be made by taking such quantities of sodium carbonate and phosphoric acid as will yield a molar ratio between NazO and P205 of 5:3, and heating this mixture to a temperature above 540 C. until the water formed by the reaction of the sodium .carbonate and phosphoric acid is driven off.

The reaction mixture is preferably allowed to cool slowly in order to obtain a fully crystalline 15 product. The materials which may be employed in accordance with the present invention for purifying gelatin and casein may be expressed by the formula M20.P2O5, in which M is hydrogen, am- 20 monium and/or an alkali-metal, and in which the molar ratio of M20 to P205 is less than 2:1. Thus, in sodium metaphosphate (NaPOa) the molar ratioof Nero to P205 is 1:1, while in so-. dium tripolyphosphate (NasPzom), it is 5:3. 25

For purposes of conciseness, I will refer to sodium metaphosphate as the material used in the purifying solution, it being understood, however, that in all cases the metaphosphatesor tripolyphosphates of the other alkali-metals or 30 of ammonium or metaphosphoric acid or tripolyphosphoric acid may be employed in place of sodium metaphosphate.

- Gelatin Gelatin is a. naturally occurring organic substance belonging to the general class known as proteins and is derived from collagen which is found in the skins and bones of animals. The uses of gelatin are very numerous, among the 40 most important of which are its use in the manufacture of glue, in the photographic industry in V the form of films, and as a food product.

Briefly described, gelatin is prepared according to prior known methods by treating the stock such as hides, sinews, bones, etc., with a saturated solution of calcium hydroxide which swells the further washing with water. The treatments yield insoluble collagen from which the gelatin is extracted by hot water. the extraction of the gelatin by hot water being generally known as the boiling process. This produces an aqueous solution of gelatin which',may be concentrated by heat or evaporation to form a solid gel which may.

moval of the calcium and by contamination with other materials in the water, such as magnesium and iron. In attempting to remove all of the lime by neutralization with acid, the gelatin may be acidified beyond the point desirable for the finished product. i

In accordance with the present invention, the stock containing the collagen or gelatin is treated with a purifying solution of sodium metaphosphate or other material of the type previously referred to, for the purpose of removing calcium, magnesium, iron and other impurities from the stock. Sodium metaphosphate combines with the calcium, magnesium or iron, forming a very slightly ionized soluble complex. The complex formed with the sodium metaphosphate where calcium is present is a very slightly ionized, s'oluble sodium-calcium metaphosphate complex.

Since this complex is soluble, the impurities removed from the stock remain in the purifying solution, which is then separated from the gelatin by decantation, filtration or other suitable method. The purified stock is then subjected tothe boiling process which extracts the gelatin.

- acid treatment may be removed by washing the ever, the metaphosphate solution may be used to replace entirely the neutralization with acid. The metaphosphate solution dissolves the alkalineearth metals, calcium and magnesium and cer tain other metals such as iron, thereby producing gelatin free from metallic ions which are generally regarded as producing an inferior or unsuitable product. Furthermore, since the purifying solution removes such substances as tend to cause cloudiness in the gelatin, the value of the gelatin, particularly for photographic purposes, is enhanced. f

The use of the metaphosphate or other "purifying solution has the further advantage that it will function at any; pH within wide limits. Hence, the pH of the purifying solution may be adjusted to any point at which the solution least affects the desired properties of thefinal product. As-illustrative of this point, the pH of gelatin greatly affects the swelling power, viscosity, etc. In order that the gelatin have optimum properties, its pH should be between 5 and 1. phosphate solution functions efiiciently within this pH range and, accordingly, does not deleteriously affect the properties of the gelatin. However, in washing gelatin with acid, the pH of the solution is markedly lower than this and there is a tendency for the final'product to have a lower pH than the optimum. The pH of a metaphosphate solution may be, adjusted to any point between 5 and 1, thus insuring complete y,

group consisting of gelatin and casein, which removal of the mineral matter without danger of affecting the pH ofthe final product or of The metahydrolyzing the gelatin. The amount of metaphosphate used depends upon the amount of impurities to be removed. Usually it is necessary to use about ten times as much by weight of metaphosphate as calcium, ,magnesium, iron, etc., which are to be removed.

Casein Casein is another organic material belonging to the class of substances known as proteins. The principal source of casein is milk, the casein being in combination with calcium. Casein is always found together with calcium, and wherever the removal of calcium, magnesium, iron, etc., whethersuch impurities are present in the origi nal material from which the casein is prepared or are present because of contamination due to the use of materials employed in the process of preparing the casein, is necessary or desirable, it may be effected with a solution of sodium metaphosphate or other material ofthe type which has been previously described.

Although I have referred specifically to the use of sodium metaphosphate as a purifying material, it is to be understood that the invention is not limited thereto, but that the other purifying materials referredito may be employed in place of the sodium metaphosphate, and that the invention may be otherwise embodied or practiced within the scope of the following claims.

I claim: a

1. The process ofpurifying a material of the group consisting .of gelatin and casein, which comprises treating said material with a solution of a compound of the formula M2O.P2O5, in which M is at least one member of the group consisting of hydrogen, ammonium and an alkali-metal, and in which the molar ratio of M0 to P205 is less than 2: 1, and separating the solution containing the impurities from the material being purified.

2. The process-of purifying a material of the group consisting of gelatin and casein, which comprises treating said material with a solution of a compound of the group consisting of alkalimetal. metaphosphate and alkali-metal tripolyphosphate, and separating the solution contain-' ing the impurities from the material being puri- 3. The process of purifying a material of the group consisting of gelatin and casein, which comprises treating said material with a solution of an alkali-metal metaphosphate, and separating the solution containing the impurities from the material being purified.

4. The process of purifying a material of the group consisting of gelatin, and casein, which comprises treating said material with a solution of sodium metaphosphate, and separating the solution containing the impurities from the material being purified.

5. The process of purifying a material of the group consisting of gelatin and casein, which comprises treating said material with a solution of sodium hexametaphosphate, and separating the solution containing the impurities from the material being purified. 1

6. The process of purifying a material of the group consisting of gelatin and casein, which comprises treating said material with a solutionof an alkali-metal tripolyphosphate, and separating the solution containing the impurities from the material being purified.

7. The process of purifying a material of the comprises treating said material with a solution of sodium tripolyphosphate, and separating the solution containing the impurities from the material being purified.

8. The process of purifying a material of the group consisting of gelatin and casein containing an alkaline earth metal compound. which comprises treating. said material with a solution of a compound of the formula Mao-P205, in which M is at least one member of the group consisting of hydrogen, ammonium and an alkali-metal, and in which the molar ratio of M20 to P205 is less than 2:1.

9. The process of purifying gelatin, which comprises treating it with a solution of an alkalimetal metaphosphate and separating the solution containing the impurities from the gelatin.

10. The process of purifying gelatin containing an alkaline earth metal compound, which comprises treating it with a solution of an alkalimetal metaphosphate and separating the solution containing the alkaline earth metal compound from the gelatin.

11. The process of purifying gelatin containing an alkaline earth metal compound, which cornprises treating it with a solution of sodium metaphosphate and separating the solution containing the alkaline earth metal compound from the gelatin.

12. The process of purifying gelatin containing an alkaline earth; metal compound, which comprises employing an alkali-metal metaphosphate solution as the final washing solution for the gelatin and separating the washing solution containing the alkaline earth metal compound from the gelatin.

13. The process of purifying casein, which com- I nesium or iron impurities-from a material of the group consisting of gelatin and casein, which comprises treating said material with a solution of a compound of the formula M2O.P2O5, in which M is at least one member of the group consisting of hydrogen, ammonium and. an alkali-metal, and in which the molar ratio of M20 to P205 is less than 2:1, and separating the solution containing the impurities from the material being purified.

16. The process of purifying gelatin containing an alkaline earth metal compound, which comprises treating it with a solution of sodium hexametaphosphate having a pH between 5 and '7, and separating the solution from the gelatin.

1'7. The process of removing calcium, magnesium or iron impurities from material of the group consisting of gelatin and casein, which comprises treating said material with a solution of an alkali-metal metaphosphate which dissolves the impurities, and separating the solution containing the impurity trom'the gelatin or casein. 

